Source of light



Jan. 6, 1931. T. w. CASE 1,788,355

SOURCE OF LIGHT Filed July 23, 1928 VENTOR W/T 33 By I H flrromrv f atented d, 1933 THEODORE WILLARD CASE, OF AUBURN, NEW YORK, ASSIGNOR TO CASE RESEARCH LABORATORY, INC., F AUBURN, NEW YORK, A CORPORATION OF NEW YORK SOURCE OF LIGHT Application filed July 23, 1928. Serial No. 294,866.

This invention relates to a certain new and improved source of light, and more particularly to a source of light for producing a photographic record of light wave variations corresponding to electrical variations, and is peculiarly adapted for producing such a record when the electrical variations correspond to sound wave variations.

The main object of the invention is to produce a more uniform, constant and instantly reactive source of light by limiting or restricting the glow about the cathode to that portion of the cathode which is provided with a coating of an alkaline earth oxide.

Other objects and advantages relate to the details of the structure and the form and relation of the parts thereof by means of which the main objectis accomplished, all as will more fully appear from the following description taken in connection with the accompanying drawings, in which:

The figure is a sectional view of a source of light of this invention.

The source of light as here illustrated comprises a bulb 1- with a stem 2 sealed therein. The electrodes may, as shown, be supported from the stem 2, and as shown the cathode 3 comprises a U-shaped wire, the opposite ends of which may be welded or 39 electrically secured to respective leads -4 and 5. The anode, as shown, is in the form of a plate 6- connected to lead -7 extending through the stem 2. The electrodes may be spaced apart a desired distanee, as for instance approximately onequarter of an inch, altho various spacing is possible.

As before suggested, it is found that a more effective light is produced if the glow about the cathode is restricted solely to that por tion of the cathode which is provided with an alkaline earth oxide coating, and in order to effect this result the opposite end portions 8-- and 9 of the U-shaped cathode 3 are enclosed by tubular members -10- and 11- respectively which may be formed of glass, and may be welded or otherwise secured to the stem 2.

These tubes 10 and 11 are of an internal diameter somewhat greater than the cross section of the wire constituting the cathode 3 and as a result the interior surfaces of the tubes 10- and 11 are spaced some distance from the respective end portions -8 and 9 of the cathode leavmg constricted annular spaces.

After this structure has been built up and assembled, as described, the cathode 3 is provided with a coating of an alkaline earth oxide. Preferably this is elfected by spreadng calcium nitrate upon the wireconstitutmg the cathode -A by means of a spatula or in any other suitable manner, and this is done for the purpose of protecting the cathode should it be formed of platinum wire, from the action of barium oxide with which the cathode is subsequently coated.

The coating of barium oxide may be produced by spreading barium nitrate upon the calcium nitrate coated cathode. These nitrates when spread upon the U-shaped cathode flow somewhat downwardly into the upper ends of the tubes 10 and 11 and when the cathode is heated, as for instance by passing a suitable electric current therethrough, the nitrate coatings become calcium oxide and barium oxide respectively, and which by subsequent heating may become sub-oxides. The oxide coating is preferably quite thick and is illustrated at -20.

In this manner all of the exposed portion of the wire constituting the'cathode 3- is provided with a coating of an alkaline earth oxide and any uncoated portions of the ends 8 and 9 of the cathode are enclosed within the tubes 10 and -11-, and as a result, when thecathode and anode are connected in circuit with a suitable source of potential, the glow which is produced about the cathode --3 will be restricted to the oxide coated portion of the wire fromv which the cathode is formed. The restricted annular spaces within the tubes --10 and --11- constituting comparatively high resistances to the existence of any glow about the uncoated portions of said wire. The bulb should be filled with an inert gas, such as preferably helium containing a small percentage of nitrogen or under certain conditions other inert gases may be used. The gas is preferably at such a-pressure that at operatmg voltage, as for instance 300 to 400 volts with 12,000 ohms in series, a highly intense glow will be concentrated about the cathode s-e arate from the anode glow.

y this method there is produced a source of light more effective for use in the production of a photographic record of light waves corresponding to electrical variations in that it is possible to coat the entire active surface of the cathode with an alkaline earth oxide or oxides, and retrict the glow which is concentrated about the cathode solely to the oxide-coated portion of the wire from which the cathode is formed.

I-claim:

1. A source of light for producing a photographic record of light wave variations corresponding to electrical variations comprisng a bulb, an inert gas Within the bulb, an anode Within the bulb, a cathode within the bulb, a tube of insulating material surrounding an end portion of the cathode and spaced therefrom and a coating comprising an alkaline earth material covering the entire exposed portion of the cathode and extending into and substantially closing the open end of 7 said tube.

2. A source of light for producing a photo- 'graphic record of light wave variations corresponding to electrical variations comprising a bulb, an inert gas within the bulb, an anode within the bulb, a cathode within the bulb and formed of a U-shaped wire having its opposite ends connected to suitable leads, tubes of insulating material surrounding but spaced from the end portions of the cathode,

and a coating comprising an alkaline earth material covering the entire exposed portion of the cathode and extending into the open ends of said tubes and substantially closing the same.

In witness whereof I have hereunto set my hand this 20th day of July, 1928.

THEODORE WILLARD CASE. 

